Automotive instrument clusters usually employ a face plate having a body of transparent light conducting material and a decorative outer applique which includes legends and indicia for gauges. Gauges mounted behind the face plate have translucent pointers which are arranged to sweep along the indicia to reveal vehicle speed, engine temperature, fuel level and other vehicle parameters. To afford visibility at night the pointers are indirectly illuminated by lamps arranged around the periphery of the face plate which conducts some the light to each pointer. Since the light sources are far away from the pointers much light intensity is lost in transition. Accordingly that scheme employs bright light sources which may consume much power. Further, due to the necessity of uniformly lighting several gauge pointers, the design of such a face plate requires substantial time and expense.
It is apparent that the elimination of such an indirect lighting system would allow a wider choice of materials for the face plate, simplifying the design of the face plate including making it thinner and, if properly executed by direct lighting, the bright light sources could be replaced by efficient low power sources which may even yield brighter pointer illumination.
Previously, applying direct lighting to conventional air core gauges has proven to be difficult in view of the presence of the gauge motor at the end of the pointer hub which is the optimum location for a light source. The size of the air core gauge dictates a thick instrument cluster assembly, and the provision of direct pointer lighting tends to further increase the size. However, in view of space limitations in vehicle dashboards, it is desirable to decrease the thickness of the instrument cluster, not increase it.